the switch to 3 naps is soooo tough isnt it!
Im so sorry you had such a disaster last night - I too had the exact same thing after i thought id finally cracked it!! I had wakings at 10pm/1am/3am/5.30am up for day at 6.30!! I also fed cos so tired!! How spooky that we both ended up in the same boat!!
sarah on the easy board had warned me that by keeping short As and long naps I would end up in an UT causing OT loop again and she was soooo right!!
I reckon thats what happened with you too...at 14 wks when they are transitioning they cant quite make the 2 hours A time so we need to slowly transition them so that means extending A time and keeping 4 naps for maybe another 3 - 6 days then going to 3 ...the nap lengths need to be shorter if you are doing 4 naps...
lets look at the whole day - if she woke at 7.30 yesterday and then had 3.5 hrs of naps then in bed by 6 pm that was only a 10.5 hr day leaving 13.5 hrs remaining in a 24 hr day cycle - do you understand what I mean!!
so 13.5 hrs night sleep wasnt ever going to happen thats what caused the UT night wakings - cos 13.5 hrs plus 3.5 naps = 17 hrs sleep total but at 3 - 4 months bubs transition to needing just 15 hrs sleep so if you want an 11 hr night sleep then you need 4 hrs of naps in day - if you want a 12 hr nightsleep you need 3 hr of naps in day...
so with 1 hr 45 A time it may need to look like this for a few days...
wake 7
nap - 8.45 - 10.15 = 1.5hrs- dont allow more than 1.5 hrs to keep on track
nap - 12 - 1.30 = 1.5 hrs
nap - 3.15 - 4 = 45 mins
nap - 5.30 - 6.15 = 45 mins
bed - 8pm
thats 4.5 total day sleep so you would then be expecting a 10.5 hr nightsleep but bear in mind she will still wake for maybe 1 - 2 feeds so you will have maybe 30 mins to an hour here so that makes wake up time hopefully 11 - 11.5 hrs after bedtime - make sense?!!

I wish I had stuck with this yesterday - instead I tried stretching him again and he took some good naps but cos I wanted to just do 3 naps but 2 of my A times were only 1 hr 45 that made my bedtime too early so too much naps into too short a day!! I should have either stretched to the full 2 hrs or done 4 naps!!
if you find she wakes early from naps then just cut 20 mins off the next A time - that should ward off any OT - then you can let her sleep the extra 20 mins ontop of that nap to keep on track...
the only problem with doing it this way is that feeds are a bit random as day progresses but im finding its actually not a feeding issue its a total sleep issue!!
how is today going?
Annette.xx